The Rio Grande river curves between low brown hills dotted with lush sub-tropical plants. Parks and wildlife refuges are scattered along the banks of the slow-moving, sinuous waters, and birdsong can be heard in the trees. It easy to forget that this is the heart of a contentious part of the world -- until you spot a big truck filled with US border control guards watching you.

Welcome to
Texas's 2,000km border zone, which makes up almost half the length of the line
separating the US and Mexico. This region has always been about how two
cultures blend rather than divide -- until recently. Uncontrolled narcotics
violence, illegal immigration and the United States' domestic politics have
driven a wedge between the nations in the last decade, with locals struggling to
adapt to the profound changes.

Nowhere are
the differences between the two sides more starkly apparent than in El Paso,
the huge city at the western end of the Texas border. On the Mexican side,
Ciudad Juarez is a sprawling city verging on anarchy, with a murder rate among
the world's worst. Yet just north of the Rio Grande, which narrows to a
concrete-lined trickle, El Paso is tied with Lincoln, Nebraska, for being the
safest city in the United States. Its near-constant sunshine bakes the traditional
adobe buildings, giving it a distinctly Hispanic feel. The city has always been
a place where the cultural currents of the border mix, which is possibly why El
Paso is home to some of the United States’ best Mexican and steak joints, such as L
& J Café and the Great
American Land and Cattle Company.

The safety
fears that have devastated cross-border tourism are barely an issue on the US
side. Thousands of Mexicans continue to cross legally into the US each day for
work and shopping. Popular Mexican restaurants and businesses have opened
outlets in Texas. In downtown Brownsville, an 800-mile drive east from El Paso,
colonial-era buildings abut the river -- yet this could be a Mexican market
town; its shops and streets buzz with day-trippers from Mexico. Its streets are
lined with myriad small businesses where it seems anything cheap is for sale,
and the chains that have homogenized the US are nowhere to be seen. Wander the
sidewalks with the bag-wielding, bargain-hunting masses, listen to Mexican pop
music blaring from stores and sample simple treats from cart-pushing food vendors.

Yet it is
the stark natural beauty and the horizon-spanning open spaces that make this
region unmissable. The truly iconic border lands are found on the long, lonely
drives through the region's majestic vastness. Remote stretches of the border,
such as east of Eagle Pass, have an uneasy desolation where hidden tensions
seem to ride the ever-blowing winds. Stories of smugglers -- both of drugs and
people -- are repeated constantly. Looking across this vast and arid landscape,
you cannot help but wonder what lurks just beyond the next lonely mesa. Drama
aside, it should be noted, the entire length of the Texas border is safe on the
US side: the huge sums spent on border guards see to that.

In the eastern
region around Brownsville, you will spot a long rusty-brown line south of Route
281 which follows the Rio Grande. It is a 200-mile stretch of the recently
built wall between the US and Mexico. At nearly seven metres tall, this
metal divide is deeply controversial: whether it is a latter day Maginot Line,
the solution to several problems or some combination of the two is hotly
debated, especially in a US presidential election year.

While the
wall's effectiveness in stopping human and drug traffic is contentious, its
effect on wildlife migration has been profound, with the tall metal structure
cutting across wildlife trails used by goats, coyotes and many other animals.
Even the birds that make this one of the richest regions in the world for twitchers
are affected. Still there is some good news, the Sabal Palm Audubon
Sanctuary, a gorgeous slice of nature on the Rio Grande east of Brownsville
reopened in 2011 after years of closure due to border politics. Change, for
better and worse, remains constant in these fascinating and troubled lands.